Some Necessary Definitions Terms May Be Misleading By definition, a perennial is a plant which lives on from year to year, not completing its life cycle in a single season as annuals do, or in two years, as with biennials. Properly applied, the term "perennial" includes trees, shrubs, and herbs. Trees and shrubs are woody; herbs die to the ground each winter. The term "herb" is loosely used by many gardeners in refer- ring to a special group of plants grown for culinary or medicinal purposes. While some of these plants are perennials, others are annuals or biennials; some are woody perennials and could not be classed as "herbs" according to the botanical definition of the word. Perennial herbs are classified in many other ways, and terms become even more confusing when we consider the special uses of plants in the garden. Some perennial herbs are grown in a place called the "wild flower garden." These may be plants that are native locally, or come from much wider geographic areas and have cultural requirements similar to the plants of the local region. Other perennial herbs either require, or will tolerate, a great deal of moisture and, when grown together in a wet place, may constitute a bog garden. Others may be low in stature or will endure hot, dry conditions. When, in various ways, they are combined with rocks or boulders and certain shrubs, they form a rock garden. Plants in all the categories above have representatives that, when planted closely under just the right conditions, grow to- gether densely and tend to discourage competition from other plants. Under these circumstances they qualify as ground covers. Obviously, perennial herbs cannot be considered always in separate categories. One group we have not discussed yet is the subject of this Handbook: the plants traditionally known as "herbaceous perennials", or just "perennials", and customarily grown in a place called the "perennial garden" or the "herba- ceous border." This group draws representatives from all the 253 254 above groups of perennial herbs, and its members are most often cultivated for their bright flowers; but plants with interesting foliage effects also are included. The very word "perennial" conjurs up the idea of permanence, and to those who would make a perennial garden the great trap is that permanence is equated all too often with ease of culture or freedom from a great deal of maintenance. In his Standard Cyclopedia of Horticulture, Liberty Hyde Bailey succinctly sums up the problem as follows: A popular fallacy about perennials lies in the common state- ment that "they die down every year and come up again in the spring." Many of them never come up again after two or three years of flowering; that is perennials are not necessarily per- petual. (our emphasis) Peonies may be as long-lived as shrub- bery, and a clump of fraxinella * has been known to outlive father, son, and grandson in the same spot. But these are ex- ceptions. The general practice with perennials is to divide them every second or third year. Nearly all hardy herbaceous plants should be lifted now and then, because the crowns that give the flowers in most desirable kinds flower only two or three seasons and then die; but the plant may be continually spreading and making new growths, which furnish the flowers, and, unless lifted and divided, the stocks become scattering and unattractive. Standards for Low Maintenance Perennials Another feature of these plants that the word "perennial" does not convey is that many have exacting requirements which must be catered to if any degree of perfection whatever is to be attained. The cultivation of several of such types together in the same garden will add up to a lot of work; certainly more work than the novice gardener, or even the experienced one with little spare time, would wish to devote. Some of the "faults" many perennials have which will necessi- tate considerable maintenance can be itemized as follows: - Short-lived. - Require annual or biennial division of the crowns. - Become invasive. - Subject to attack by insects or diseases. ^ Dictamnus albus, the Gas Plant 255 - Need staking and tying to prevent flopping. - Foliage does not remain attractive during the entire grow- ing season. - Tolerate only a very narrow range of growing conditions with regard to soil, moisture, or light. - Not fully hardy. Possession of any of the above "faults", with the exception of the last, is probably not sufficient reason in every case to ban particular plants from the garden, even when the standard for minimal maintenance is a priority. If this were so, the list of perennials that could be grown would be a scanty one in- deed ! It is when certain plants combine two or more of these "faults" that they may be regarded as requiring considerable maintenance. To look on the brighter side, there are many perennials that possess the endearing qualities of ease of culture, a relatively long life, and freedom from insects and diseases. However, the gardener who lacks years of experience faces the very consider- able problem of selecting these from amongst the many hun- dreds of varieties available from nurseries. Catalogs are no- torious for their glowing descriptions of flower color, or any other good attribute a plant may possess; however, information about the amount of work necessary to produce a dazzling dis- play or the life expectancy of a plant is mighty scanty. This is not meant to discredit the nurserymen. In general, American nurseries are doing a fine job of offering the better species or selections to a very heterogeneous group of gardeners. Textbooks too, are not always the most convenient sources of information about low maintenance perennials. They often tend to be encyclopedic in nature - some even include varieties that are completely unavailable from nurseries. For the average reader it thus becomes tedious to select those plants that are easiest to grow from the numerous varieties described, and the lengthy cultural formulae provided. In this discussion we wish to draw attention to the perennials that will require the least amount of maintenance. We know of no desirable plant, however, that can be expected to thrive in the garden without some form of attention. This handbook, 256 I therefore, should not be considered a "lazy man’s guide" to peren- nials. The standards we have selected that qualify a plant as "easy" in the ensuing text are as follows: - Will not require division for about four years under normal circumstances; some can go much longer. - Perfectly hardy in the Boston area, though some form of winter protection is advisable for most perennials. (In this category we also place resistance to summer heat as a type of hardiness.) - Immune to, or tolerant enough of, insect and disease prob- lems so that spraying usually will not be necessary. - Stems sufficiently sturdy so that staking may be avoided under most circumstances. - Tolerant of a fairly wide variety of soil types and condi- tions. - Foliage remains in acceptable condition through the grow- ing season. If not, it dies down quickly and may be masked by surrounding plants. In applying these standards, we banish some of the showiest of all perennials. Gone are the hybrid Delphiniums, most of the hardy Chrysanthemums, and Phloxes, Lupines, or Carnations, and many others traditional to the perennial garden. But how many traditional perennial gardens do we see nowadays? In our hurried times, perennials have come into some measure of disfavor because a few of the more famous ones are the most difficult to grow. People have tried them, have had good results only temporarily, and have given up altogether. Recommended Perennials for Low Maintenance The perennials we recommend for ease of culture are described in this chapter. Representatives of most all the major groups discussed here have been tried at one time or another at the Case Estates of the Arnold Arboretum in the area known as the Low Maintenance Garden. This garden is situated in a frost pocket where winter temperatures may drop to -20° F, or lower. Soil conditions in some parts of the garden are very moist, especially during the winter months, and some perennials are either killed or heaved out of the ground during alternate periods of freez- ing and thawing. Some sections of the garden receive full sun all day, while others remain either in partial or deep shade. Thus we have been able to observe and record the perfor- mance of many perennials under adverse, and frequently poor, growing conditions. We make the basic assumption that a plant which has performed well for several years in the Low Mainte- nance Garden can be grown in most gardens in the Boston area, and often considerably further north. In order that gardeners may make intelligent choices when selecting their plant materials, we discuss in alphabetical order most all the major genera of perennials offered by the nursery trade. Those that qualify as "easy" plants, and are especially recommended as low maintenance subjects, occupy the main body of the text. Those which are of secondary value (or of no value at all where low maintenance is concerned) are included, but set apart in smaller type. This secondary listing is in no way meant to condemn the groups of plants involved. As already stated, some of the most beautiful perennials belong in these groups. If a gardener has selected mainly the recommended plants, he then may have the time to cater to the needs of a few of the more demanding types if he so desires. We have attempted to provide as many sources as possible for each plant discussed.